In a synchronous optical network (SONET) network element (NE), incoming synchronous payload envelope (SPE) data are loaded into buffers upon arrival. When a switch fabric requests SPE data for a channel, the SPE data is retrieved from the channel's buffer, and loaded into a cell payload data unit (PDU) for transmission to and across the switch fabric. If there is insufficient SPE data in the buffer to fill the cell PDU, then nothing is sent to the switch fabric at that time. Since the stream of incoming SPE data arrives asynchronous with the switch fabric operation, such a retrieval and cell loading mechanism may cause undesirable jitter in the SPE data stream received on the outgoing side of the switch fabric.